Organization:365 Days Of Astronomy
Description: Space scoop, news for children
Our understanding of Saturn’s rings is still evolving. A team of researchers using observations made in 2008 have managed to measure the brightness and temperature of Saturn’s rings in more detail than ever. More detail in mid-infrared images from the ground, that is.
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Bio: Richard Drumm is President of the Charlottesville Astronomical Society and President of 3D – Drumm Digital Design, a video production company with clients such as Kodak, Xerox and GlaxoSmithKline Pharmaceuticals. He was an observer with the UVa Parallax Program at McCormick Observatory in 1981 & 1982. He has found that his greatest passion in life is public outreach astronomy and he pursues it at every opportunity.
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This is the 365 Days of Astronomy Podcast. Today we bring you a new episode in our Space Scoop series. This show is produced in collaboration with Universe Awareness, a program that strives to inspire every child with our wonderful cosmos.
Saturn’s Rings Are Warm and Fuzzy
If you go outside on a dark, cloudless night, you could see up to six planets without a telescope. Mercury, Venus, Mars, Jupiter and Saturn and even distant Uranus can all be seen by the naked eye.
You have to be in a particularly dark site to see Uranus with the naked eye, though, it’s very dim.
The planets have fascinated people for thousands of years, yet it wasn’t until the invention of the telescope that Saturn’s spectacular rings were first seen.
It was Galileo Galilei in 1610 who first saw the rings, but he thought they looked like 2 moons on each side of the planet, like 2 people helping an old grandpa walk along.
The astronomers of the day were quite perplexed by the changing appearance of the planet. It was the changing tilt of the rings as seen in the low quality telescopes of that era that caused the confusion.
Sometimes it looked like 2 moons that didn’t move about the planet like Jupiter’s moons do. Sometimes it looked like 2 teacup handles. And then adding to the mystery was the fact that the rings would periodically align with Earth and disappear altogether.
It was quite the mystery for decades!
It took Christiaan Huygens in 1655 to use a better telescope to see that the ring was, in fact, a ring. It was in 1659 that he finally published his solution. In his words, translated to English, it was: “a thin, flat ring, nowhere touching, and inclined to the ecliptic.”
It would be another 330 years before really detailed photographs of the rings were taken when the Voyager spacecraft visited the planet in the 1980s.
We already knew that Saturn had seven large rings, separated by empty gaps called ‘divisions’. But the spacecraft revealed that Saturn actually has thousands of rings.
The rings are made up of billions of bits of ice and rock, ranging in size from tiny, dust-sized grains to particles as large as a tractor-trailer truck. The thickness of the rings ranges from only 10 meters, or 30 feet thick to a kilometer or two thick.
But our understanding of Saturn’s rings is still evolving. A team of researchers using observations made in 2008 have managed to measure the brightness and temperature of Saturn’s rings in more detail than ever. More detail in mid-infrared images from the ground, that is.
And the ground the telescope sits on is Mauna Kea on the island of Hawaii. The instrument the IR light was detected with was COMICS, the COoled Mid-Infrared Camera and Spectrometer on the Subaru North telescope which is operated by the NAOJ, the National Astronomical Observatory of Japan.
They found that the C ring, the dark part of the visible ring that is closest to the planet, appeared much brighter than its two neighboring rings in these infrared thermal images, exactly opposite to its appearance in visible light.
In visible light the A &B rings are the bright ones. But in IR the bright one is the C ring. This means that the C ring is warmer than the A & B rings.
Strangely a gap called the ‘Cassini Division’ between the A & B rings also shone brightly in the thermal images, revealing that it’s more than just an empty space between rings.
We think these regions are warmer because they contain fewer particles, making it easier for the Sun to heat what little is there. Plus, the particles are darker and therefore absorb more heat.
On the other hand, the Cassini division looks basically empty in normal, visible light images. While the neighboring rings have more particles to reflect sunlight and therefore appear brighter.
Hey, Here’s A Cool Fact:
These 2 parts that shine brightly in IR don’t always do so. By looking back at IR observations from 3 years earlier they found a 15 year cycle in the brightness that corresponded to the tilt of Saturn’s rings relative to the Sun.
Because Saturn’s rings are tilted relative to its orbit around the Sun, during part of its orbit the north side of the rings is bathed in sunlight. Then for the other half of its approximately 29 1/2 year orbit the south side gets the sunlight.
So it seems Saturn’s rings have seasons!
Thank you for listening to the 365 Days of Astronomy Podcast!
End of podcast:
365 Days of Astronomy
The 365 Days of Astronomy Podcast is produced by Astrosphere New Media. Audio post-production by Richard Drumm. Bandwidth donated by libsyn.com and wizzard media. You may reproduce and distribute this audio for non-commercial purposes. Please consider supporting the podcast with a few dollars (or Euros!). Visit us on the web at 365DaysOfAstronomy.org or email us at info@365DaysOfAstronomy.org. This year we will celebrate more discoveries and stories from the universe. Join us and share your story. Until tomorrow! Goodbye!